1. Field of the Invention
The present invention relates generally to an apparatus and method for a Base Station (BS) of a wireless communication system to perform an auction process on the basis of bidding prices presented by Relay Stations (RSs), to select one or more RSs to operate in an active mode.
2. Description of the Related Art
With the development of mobile communication systems, services essentially requiring communication environments of good quality are on the increase. To enable such services, research is being conducted to introduce the concept of intra-cell RSs.
In general, RSs are used to provide cell coverage improvement, Signal to Interference plus Noise Ratio (SINR) improvement, and inter-RS cooperative communication.
Such RSs are generally installed in intra-cell shadow areas or at cell boundaries to amplify/transmit or retransmit signals from BSs to user terminals (or Mobile Stations (MSs)) that are located in shadow areas incapable of receiving services from the BSs even with high power.
Even in the shadow areas wherein MSs are incapable of receiving good services from BSs, MSs can receive services through RSs capable of amplifying/transmitting signals between links, thereby improving the link qualities. Such RSs can be used for the next-generation mobile communication services (e.g., BWA communication services) that require the transmission of large amounts of data.
Institute of Electrical and Electronics Engineers (IEEE) 802.16j standard is being developed as the technical standard for the implementation of such RSs. The IEEE 802.16j standard specifies a sleep mode of an RS. This deactivates the RS in the case where there is no MS to serve, thereby enabling the RS to automatically turn on/off its own transmit/receive (TX/RX) power in such a case. However, the IEEE 802.16j standard does not specify which MSs will be served by the RS, that is, a collection of target MSs of the RS.
The RS may select some of MSs in its coverage area. In this case, if the selected MSs have relatively poor channel conditions, setting all the selected MSs to communicate through the RS may cause problems.
Also, because the next-generation mobile communication services may have diverse Quality-of-Service (QoS) requirements, setting communication links without taking into consideration such diverse QoS requirements may reduce the QoS satisfaction levels.
If there is an MS communicating with a BS at a low RX data rate with a small delay, the MS may or may not be satisfied with the quality of a link with the BS, depending on its current service type.
There is no method for a conventional RS to select MSs. If such a conventional RS is configured to set an MS to communicate through the conventional RS, without knowing whether the MS is satisfied with the QoS, the use of the conventional RS may reduce the QoS satisfaction level of the user, contrary to expectation.
If possible, it is recommended that all the intra-cell areas should become Line-Of-Sight (LOS) environments in the next-generation communication environments requiring higher-quality channel conditions. Thus, it is required that RSs are installed throughout the cells.
However, if many RSs operate in the neighborhood of the boundary of a cell and thus increase the power in the neighborhood of an adjacent cell, this increases the interference with the adjacent cell (in comparison with the case of using only BSs for communication services), thus reducing the QoS satisfaction levels of the users in the adjacent cell.